Defender is an arcade video game developed and released by Williams Electronics in February 1981. A shooting game featuring two-dimensional (2D) graphics, the game is set on a fictional planet where the player must defeat waves of invading aliens while protecting astronauts. Development was led by Eugene Jarvis, a pinball programmer at Williams; Defender was Jarvis' first video game project and drew inspiration from Space Invaders and Asteroids. Williams planned to display the game at the Amusement & Music Operators Association (AMOA) trade show, though development delays resulted in the team working on the game up until the show started.

Defender was one of the most important titles of the Golden Age of Video Arcade Games, selling over 55,000 units to become the company's best selling game and one of the highest-grossing arcade games ever. Praise among critics focused on the game's audio-visuals and gameplay. It is frequently listed as one of Jarvis' best contributions to the video game industry, as well as one of the most difficult video games. Defender was ported to numerous platforms, inspired the development of other games, and was followed by sequels and many imitations.

Defender is a two-dimensional side-scrolling shooting game set on the surface of an unnamed planet. The player controls a space ship as it navigates the terrain, flying either to the left or right. A joystick controls the ship's elevation, and five buttons control its horizontal direction and weapons. The object is to destroy alien invaders, while protecting astronauts on the landscape from abduction. Humans that are successfully abducted return as mutants that attack the ship. Defeating the aliens allows the player to progress to the next level. Failing to protect the astronauts, however, causes the planet to explode and the level to become populated with mutants. Surviving the waves of mutants results in the restoration of the planet. Players are allotted three chances (lives) to progress through the game and are able to earn more by reaching certain scoring benchmarks. A life is lost if the ship comes into contact with an enemy or its projectiles. After exhausting all lives, the game ends.

SPECIAL NOTES ON THE OPERATION OF DEFENDER IN THE BROWSER:

Defender is a particularly difficult game to play, both in the original Arcade version and especially in this browser-based edition. Here are some basic tips:

First, all Williams games of this era require the "ADVANCE" button to be pressed after the game has booted and in Operator Mode. You can press F2 on your keyboard (although many browsers will not understand you pressing F2 or try to do other actions), or you can use the virtual keyboard next to the screen to press the "ADVANCE" button. At this point, the game will be in attract mode and playable.

Next, the controls to Defender were unusually difficult for the time, and continue to be involved. They are:

• UP and DOWN arrows to move your ship up and down the screen
  
• ALT/OPTION to thrust your ship
  
• CONTROL to fire
  
• SPACE to fire a "Smart Bomb"
  
• SHIFT to go into Hyperspace
  
• Z for Reverse
  

If you'd like to change these settings, press TAB and go to Input (This System) to make changes - please bear in mind these changes will disappear when you close your browser.